[74chevyflat]

hey guys i have unshrouded my valves on my heads finally and been debating on how i can gain back the compression. but seeing as how i am still using non adjustable rocker arms. I thought to myself about the turbo i have stored away and a 2 brrl rochester 500 carburetor.

But in the meantime i have just ru accross a eaton-m-90 supercharger for a 3.8 pontiac. the guy said he was using a holley carburetor as a draw through. i was wondering could i match al of this together somehow? should go with bigger valves, and what camshaft should i install. i have some options on www.streetperformance.com. and summit racing. just wondering would a comp cam 260adv 212@ .440/.440 @110 lobe seperation work?

[74chevyflat]

i was doing some checking and ill have to fab the intake tubing to the log manifold.this particular supercharger has a boost pressure releif valve. my question would be seeing as how im gonna use it as a draw through umm.. doesn't the waste boost include fuel? could i reroute the waste vent to the intake on the carburetor? stock for of this superC. makes 6 lbs of boost on a 3.8l v-6. ive seen on classicinlines,com in the photo album of an install like this minus the carb running straight fuel injection with the aluminum head.

Does anyone have any sayso on this>? If so please comment. need some help here deciding wether i CAN do this and be successful . thanks allot

[techinspector1]

In my opinion, anything can be made to work on anything.

I've toyed with this idea in the past and if I were going to pull fuel through the blower, I would want to make sure that all the gaskets, seals and bearings were gasoline-proof. These blowers were designed to pass only dry air, so I would want to know.

Of course, a guy could still use it to pump only air and blow through a prepared carburetor, like in a turbo blow-through application. Call up these guys or email them and yank their chains for info on carb mods....
http://www.csucarbs.com/
http://www.candsspecialties.com/

Here is an article on blow through....
http://www.theturboforums.com/smf/in...topic=136075.0
And here's the turbo forum with blow through info....
http://www.theturboforums.com/smf/index.php?board=13.0

[74chevyflat]

thank u very much sir. i appreciate the info. ill check up on modifying my carb. which would u say would be better on such a small cubic inch engine a rochester 2gc , stock 1 brrl or a holley 4brrl. i know i should look for a holley 2300 series. its the best there is for tuning / modifying. and repair parts and kits are readily available. but as of what i do have what would u say would be best.

[66GMC]

This sounds like a very interesting project!

I've got a 1998 Pontiac GTP 3.8 with that little blower on it and just love it.

I stumbled upon a thread in another forum where a guy was using an M90 on a 302/351W full-size Bronco ... and he seems to know his stuff. He was talking about using a surge valve and recycling the air / fuel mix to the inlet side of the charger rather than discharging it to the atmosphere.

It was a little over my head, but perhaps it will make more sense to you?

[techinspector1]

I would think that the fellows I gave you links to would be more apt to have modified a Holley 4-bbl, so that one might be easier or less money to modify. Making or modifying a manifold to fit it might be a little more challenging, but I would think that the results would justify the work.

I also wouldn't worry with bigger valves or more cam. If you blow 6 psi into the motor, you're gonna think you changed motors to a V8.

[matt167]

a member on www.fordsix.com had a 3.8 thunderbird Eaton M90 on a 200 set up draw thru and it worked good, but the engine did give out eventually from over boost

[techinspector1]

Originally Posted by matt167

but the engine did give out eventually from over boost

Yep, it's the old hot rodder's axiom...
"If some is good, more is better and too much is just right".

[matt167]

yep. as I recall, it was boosting on 10 PSI when it went, but with the 5-6 psi stock pully, it held until it was upgraded.. no doubt, with forged pistons, it would have held. there are 200's cranking over 300+ hp off turbo's, and 250's cranking 400+

[74chevyflat]

what are the modifications needed on corburetordiffering from draw though and blow through? what fuel pump is needed for either. pressure gph? and how do i keep the carb from blowing the gaskets. and should i helicoil the carb with bigger bolt to torque them down tighter? and about the exhaust. could i make a staged header. biggerpipe to smaller pip from port to port downsizing as it goes? ive seen one in classicinlines done like this. wold it work on a NA engine? and yeild better than headers?

[66GMC]

Converting a carburetor to a "blow-thru" would be a real PITA, IMHO.
There are just so many things in a carb that expect to see atmospheric pressure, not boost.

[74chevyflat]

so lets say i use a 264 singe pattern camshaft and the m90 with a 600 pull through . now this carburetor what settings or modifications does it need?

[matt167]

boost refrence the power valve..

it's not hard to make a blow thru carb out of a basic Holley.. remove choke and choke lever. expoxy lever hole shut. install nitrophotyl float and for many engines your done. others may need drilled air bleeds... blow thru does need to have fuel preassure rise on a 1:1 basis, but the holley projection electric fuel pump ( really a Waleboro )with a boost refrenced bypass fuel preassure regulator works fine

[74chevyflat]

is there any wesite that explains this in detail for a ""holley two brrl"" carburetor?

[74chevyflat]

this is the regulator i can use. now to the holley 2 brrl mods. still digging into different forums and sites.